use relative paths to avoid invalid redirect to generic.html, fix bad…

[otykier]

1. After the multi-language migration, index.html lives at /en/whats-new/index.html
2. The JavaScript on line 109 makes an XHR to an absolute path: /whats-new/generic.html (no /en/ prefix)
3. The build process (generate_lang_prefix_redirect_pages) creates a redirect stub at /whats-new/generic.html
   containing
4. The XHR gets back this meta-refresh HTML and injects it into the DOM via innerHTML
5. The browser follows the meta-refresh and navigates to /en/whats-new/generic.html directly — losing all the
   layout/JS from index.html

The fix is to change the absolute path to a relative one so it resolves correctly under /en/whats-new/

Also fixed bad UTF-8 chars in some .html files

[github-actions]

Azure Static Web Apps: Your stage site is ready! Visit it here: https://delightful-mud-081affe03-274.westeurope.azurestaticapps.net

[otykier]

The fix seems to work.

Compare:

https://delightful-mud-081affe03-274.westeurope.azurestaticapps.net/whats-new

to

https://docs.tabulareditor.com/whats-new